As a system for protecting an occupant in the event of a car collision, a system is proposed in which the front part of a seat cushion is pushed up in a car collision to prevent a submarine phenomenon such that the occupant passes under a lap belt during a front crash even with a seatbelt. For example, Japanese Unexamined Patent Application Publication No. 10-217818 describes a vehicle seat in which the front end of the seat cushion is pushed up by an airbag.
It is known in the art to provide an air belt system (inflating seatbelt system) as an occupant protection system (for example, Japanese Unexamined Patent Application Publication No. 2003-312439). In the air belt system of the reference, both of a shoulder belt and a lap belt are inflatable. To the inflatable shoulder belt and lap belt, gas from a gas generator disposed to a buckle is introduced through a tongue. The tongue and the buckle each include a gas supply passage for supplying the gas from the gas generator to the shoulder belt and the lap belt.
Furthermore, Japanese Unexamined Patent Application Publication No. 2002-145002 discloses an occupant protection system in which a seat bag at the front of a seat back, a shoulder belt, and a lap belt are inflated to protect an occupant. The reference shows a structure in which the seat bag at the front of the seat back, the shoulder belt, and the lap belt are inflated by one gas inflator.
In the occupant protection system of Japanese Unexamined Patent Application Publication No. 2002-145002, one end of the inflatable shoulder belt and one end of the inflatable lap belt are joined with different tongues, respectively. The shoulder belt and the lap belt are latched by a buckle unit via the tongues, respectively. The buckle unit and the tongues have gas supply passages for supplying gas from the gas generator to the shoulder belt and the lap belt.
The occupant protection systems disclosed in Japanese Unexamined Patent Application Publication Nos. 2003-312439 and 2002-145002 require a tongue having a gas supply passage, a buckle unit having a gas generator and a passage for introducing gas from the gas generator, and a coupler for detachably joining the tongue-side gas supply passage and the buckle-side gas supply passage, so that the tongue-buckle mechanism is complicated. Also it needs cover means for preventing entry of foreign matter such as dust into the gas supply passage and the gas inlet passage, so that it has a complicated structure.